Zirconium tin titanate compositions, ceramic bodies comprising same, and methods of manufacturing same

ABSTRACT

Disclosed is a microcracked ceramic body, comprising a predominant phase (greater than 50 wt %) of zirconium tin titanate and a dilatometric coefficient of thermal expansion (CTE) from 25 to 1000 C of not more than 40×10−7° C.−1 as measured by dilatometry and methods for the manufacture of the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application under 35 U.S.C. § 371of International Patent Application Serial No. PCT/US2016/054103, filedon Sep. 28, 2016, which claims the benefit of priority under U.S.Provisional Application Ser. No. 62/233,736 filed on Sep. 28, 2015, thecontents of are relied upon and incorporated herein by reference intheir entireties.

BACKGROUND Field

Exemplary embodiments of the present disclosure relate to ceramic bodiesand methods of manufacturing the same and, more particularly, tomicrocracked ceramic bodies including a zirconium tin titanate phase,and methods of manufacturing the same.

Discussion of the Background

Materials for use in high-temperature applications that are subject tothermal gradients require thermodynamic stability under use conditions;resistance to oxidizing and, in some cases, reducing atmospheres; highmelting point; minimal change in dimensions after many thermal cycles;and high thermal shock resistance, usually by virtue of a lowcoefficient of thermal expansion (CTE). The number of ceramic materialswhose properties satisfy these requirements can be limited, andinstances can occur in which other demands of the applicationnecessitate certain other specific properties of the ceramic material.For example, in applications related to engine exhaust after-treatment,the ceramic must possess chemical durability in the presence of othermetal oxides that may be either applied to the ceramic to enhance itsfunctionality (for example, catalysts) or come into contact with theceramic as a component of the external environment (for example, ashfrom combustion of impurities or additives in fuels).

The above information disclosed in this Background section is only forenhancement of understanding of the background of the disclosure andtherefore it may contain information that does not form any part of theprior art nor what the prior art may suggest to a person of ordinaryskill in the art.

SUMMARY

Exemplary embodiments of the present disclosure provide a ceramic bodycomprising a predominant phase of zirconium tin titanate.

Exemplary embodiments of the present disclosure also provide a method ofmanufacturing a ceramic body comprising a predominant phase of zirconiumtin titanate.

Additional features of the disclosure will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the disclosure.

An exemplary embodiment discloses a microcracked ceramic body,comprising: a predominant phase of zirconium tin titanate; a microcrackdensity; and a dilatometric coefficient of thermal expansion (CTE) from25 to 1000° C. of not more than 40×10⁻⁷° C.⁻¹ as measured bydilatometry.

Another exemplary embodiment discloses a method of manufacturing amicrocracked ceramic body. The method comprises providing an inorganicbatch composition comprising a zirconium oxide powder, a titanium oxidepowder, and a tin oxide powder, wherein the median particle size of atleast two of the oxide powders is at least 5 μm and wherein the sum ofthe weight percentages of the zirconium oxide powder, titanium oxidepowder, and tin oxide powder is sufficient to provide more than 50weight percent of a zirconium tin titanate phase in the microcrackedceramic body. The method comprises mixing the inorganic batchcomposition together with one or more processing aids selected from thegroup consisting of a plasticizer, lubricant, binder, pore former, andsolvent, to form a plasticized ceramic precursor batch composition, andshaping the plasticized ceramic precursor batch composition into a greenbody. The method comprises firing the green body under conditionseffective to convert the green body into the microcracked ceramic bodycomprising a predominant phase of zirconium tin titanate. The mol % ofeach of ZrO₂, SnO₂ and TiO₂ components in the zirconium tin titanatephase is expressed as 40≤Z≤65, 13≤S≤50, and 5≤T≤30, where Z=100(mol %ZrO₂)/(mol % ZrO₂+mol % SnO₂+mol % TiO₂), S=100(mol % SnO₂)/(mol %ZrO₂+mol % SnO₂+mol % TiO₂), and T=100(mol % TiO₂)/(mol % ZrO₂+mol %SnO₂+mol % TiO₂), a minimum lattice CTE (CTE_(min)) from 25 to 1000° C.of the zirconium tin titanate phase is not more than 30×10⁻⁷° C.⁻¹, anda zirconium tin titanate grain size parameter, g, in units ofmicrometers (μm) isg≥k₂[4.15+1.99×10⁶(CTE_(min))+3.58×10¹¹(CTE_(min))²+2.15×10¹⁶(CTE_(min))³],wherein k₂≥CTE_(min) is in units of ° C.⁻¹, and the grain size parameteris determined by a line intercept method applied to an image of theceramic microstructure and is defined as g=L/p where p is the number ofgrain boundaries intercepted by one or more straight lines of totallength L or one or more circles of total circumference L, wherein L isin units of micrometers and L is chosen such that the value of L/g is atleast 25 in order to provide adequate counting statistics forcalculation of the grain size parameter.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the disclosure.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of thedisclosure, and together with the description serve to explain theprinciples of the disclosure.

FIG. 1 depicts the approximate phase relations in the ZrO₂—TiO₂—SnO₂system at 1500-1600° C. as determined by the present investigation,including the approximate limits of the composition of the zirconium tintitanate phase (ZrTiO₄ solid solution (ss)), zirconium oxide phase (ZrO₂(ss)), and tin oxide-titanium oxide (cassiterite-rutile) phase (SnO₂(ss) and (Sn,Ti)O₂ (ss)). All compositions are in mole percent. Phasecomposition boundaries are denoted by solid curves. Solid and dashedlines indicate approximate orientations of tie lines joining thecompositions of coexisting phases.

FIG. 2 shows the compositional limits A-B-C-D-E-F of the zirconium tintitanate phase in exemplary embodiments of the present disclosure, on amole percent basis, projected onto the ZrO₂—TiO₂—SnO₂ ternarycompositional diagram (sum of mole percentages of ZrO₂, TiO₂ and SnO₂components in the zirconium tin titanate phase normalized to 100%).

FIG. 3 shows the compositional limits G-H-I-J-K-L of the zirconium tintitanate phase in other exemplary embodiments of the present disclosure,on a mole percent basis, projected onto the ZrO₂—TiO₂—SnO₂ ternarycompositional diagram (sum of mole percentages of ZrO₂, TiO₂ and SnO₂components in the zirconium tin titanate phase normalized to 100%).

FIG. 4 shows the compositional limits M-N-O-P-Q-R of the zirconium tintitanate phase in preferred exemplary embodiments of the presentdisclosure, on a mole percent basis, projected onto the ZrO₂—TiO₂—SnO₂ternary compositional diagram (sum of mole percentages of ZrO₂, TiO₂ andSnO₂ components in the zirconium tin titanate phase normalized to 100%).

FIG. 5 is a plot of the microcrack index, Nb³, of the ceramic bodyversus the minimum lattice axial coefficient of thermal expansion(CTE_(min)) from room temperature (RT) to 1000° C. of the zirconium tintitanate phase. Filled symbols denote examples fired at 1600° C., opensymbols denote examples fired at 1400° C., circles denote exemplarybodies of the disclosure, squares denote comparative bodies. Data arefor Nb³ determined by image analysis. The boundary denoted by the solidcurve defines the lower limit for the microcrack index required toachieve a dilatometric CTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹, corresponding toEq. 6 with k₁=1.0. Other boundary curves correspond to values of k₁=1.5(dash-dotted), 2.0 (long dashed), 2.5 (short dashed), and 3.0 (dotted).Dashed vertical line denotes the maximum limit for CTE_(min) of thezirconium tin titanate phase.

FIG. 6 is a plot of the grain size parameter (average linear interceptlength) of the zirconium tin titanate phase versus the minimum latticeaxial CTE (CTE_(min)) of that phase. Filled symbols denote examplesfired at 1600° C., open symbols denote examples fired at 1400° C.,circles denote exemplary bodies of the disclosure, squares denotecomparative bodies. The boundary denoted by the solid curve defines thelower limit for the grain size parameter required to achieve adilatometric CTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹, corresponding to Eq. 8with k₂=1.0. Other boundary curves correspond to values of k₂=1.25(dash-dotted), 1.50 (long dashed), 1.75 (short dashed), and 2.0(dotted).

FIG. 7 displays the compositions of the zirconium tin titanate phase inexemplary embodiments of the disclosure (solid circles) and comparative(open circles) examples fired at 1500° C. (Table 3) in terms of the molepercentages of the ZrO₂, TiO₂, and SnO₂ components in the zirconium tintitanate phase normalized to 100%. Numbers indicate dilatometric CTEfrom 25 to 1000° C. Polygon denotes preferred exemplary compositionallimits from FIG. 2.

FIG. 8 displays the compositions of the zirconium tin titanate phase inexemplary embodiments of the disclosure (solid circles) and comparative(open circles) examples fired at 1600° C. (Table 4) in terms of the molepercentages of the ZrO₂, TiO₂, and SnO₂ components in the zirconium tintitanate phase normalized to 100%. Numbers indicate dilatometric CTEfrom 25 to 1000° C. Polygon denotes preferred exemplary compositionallimits from FIG. 2.

FIG. 9 is a plot of the Young's elastic modulus versus temperatureduring heating (filled circles) and cooling (open squares) ofcomparative Example D6a. E₂₅° is denoted by the open circle and is thevalue of the tangent line to the linear section of the cooling curvefrom 650 to 1000° C. extrapolated to room temperature.

FIG. 10 is a plot of the Young's elastic modulus versus temperatureduring heating (filled circles) and cooling (open squares) of exemplaryExample M6a. E₂₅° is denoted by the open circle and is the value of thetangent line to the linear section of the cooling curve from 500 to1200° C. extrapolated to room temperature.

FIG. 11 is a plot of ΔL/L versus temperature on heating and thepredicted thermal shock limit for comparative Example D6a of about 100°C.

FIG. 12 is a plot of ΔL/L versus temperature on heating and thepredicted thermal shock limit for exemplary Example F6a of nearly fourtimes the predicted thermal shock limit for comparative Example D6a.

FIG. 13 is a plot of ΔL/L versus temperature on heating and thepredicted thermal shock limit for exemplary Example M6a of over fourtimes the predicted thermal shock limit for comparative Example D6a

FIG. 14 is a plot of ΔL/L versus temperature on heating and thepredicted thermal shock limit for exemplary Example P6a of nearly fourtimes the predicted thermal shock limit for comparative Example D6a.

DETAILED DESCRIPTION

It will be understood that for the purposes of this disclosure, “atleast one of X, Y, and Z” can be construed as X only, Y only, Z only, orany combination of two or more items X, Y, and Z (e.g., XYZ, XY, YZ,XZ).

Among refractory oxide materials, zirconium titanate, ZrTiO₄, hasreceived attention for its dielectric properties since the 1940s, and inthe 1970s it was discovered that further improvement in dielectricproperties could be gained through the partial substitution of tin(Sebastian, M. T. (2010) Dielectric Materials for Wireless Communication(Chapter 4—Zirconium Tin Titanate), Elsevier, Oxford, UK). The limit oftin solubility in the zirconium titanate phase at high temperatures wasdetermined by several studies in the 1980s (Wolfram, G. and Goebel, H.E. (1981) “Existence range, structural and dielectric properties ofZr_(x)Ti_(y)Sn_(z)O₄ ceramics (x+y+z=2),” Mat. Res. Bull., 16,1455-1463; Wilson, G. and Glasser, F. P. (1989) Solid solution in theZrO₂—SnO₂—TiO₂ system, Br. Ceram. Trans. J., 88 [3] 69-74). Theapproximate phase relations and extent of solid solution of thezirconium tin titanate phase at 1500-1600° C. determined by the presentinvestigation is shown in FIG. 1.

Although ZrTiO₄ is known to have a melting point in excess of 1800° C.(Coughanour, L. W., Roth, R. S., DeProsse, V. A. (1954) PhaseEquilibrium Relations in the Systems Lime-Titania and Zirconia-Titania,Journal of Research of the National Bureau of Standards, 52 [1] 37-42),its very high coefficient of thermal expansion precludes its use inthermal shock environments. Ikawa et al. (Ikawa et al. (1988) “PhaseTransformation and Thermal Expansion of Zirconium and Hafnium Titanatesand Their Solid Solutions” J. Am. Ceram. Soc. 71 [2] 120-127) preparedpolycrystalline bodies of ZrTiO₄ by co-precipitation of mixed oxides andreaction sintering of the powders at 1600° C., and determined the CTE(RT—1000° C.) to be 81×10⁻⁷° C.⁻¹ by dilatometry. Bayer et al. (Bayer etal. (1991) “Effect of Ionic Substitution on the Thermal Expansion ofZrTiO₄ ” J. Am. Ceram. Soc., 74 [9] 2205-2208) reacted mixtures of finemetal oxides to form ZrTiO₄ at 1600° C. and similarly found thecoefficient of thermal expansion (25-1000° C.) of the ceramic body to be82×10⁻⁷° C.⁻¹. It was also found that the CTE of zirconium titanateceramics could be reduced by the substitution of tin. Thus, Ikawa et al.(1988) reported the CTEs of Zr_(0.7)Sn_(0.3)TiO₄ andZrTi_(0.4)Sn_(0.6)O₄ ceramics to be 68 and 48×10⁻⁷° C.⁻¹, respectively,while Bayer et al. (1991) determined the CTE of a ZrTi_(0.5)Sn_(0.5)O₄ceramic to be 68×10⁻⁷° C.⁻¹ and that of a ZrTi_(0.4)Sn_(0.6)O₄ body tobe 48×10⁻⁷° C.⁻¹, all as measured by dilatometry.

Despite reduction in the CTE of zirconium titanate by the substitutionof tin demonstrated in the prior art, CTE values remain higher thandesired for use in thermal shock environments. A further reduction inthe mean CTE from 25-1000° C. to less than 40×10⁻⁷° C.⁻¹, and even morepreferably less than 30×10⁻⁷° C.⁻¹, in zirconium tin titanate ceramicbodies would promote their consideration as new highly refractorymaterials for thermal shock applications.

Exemplary embodiments of the present disclosure relate to microcrackedceramic bodies (articles) comprising a predominant phase of zirconiumtin titanate and having a mean coefficient of thermal expansion over thetemperature interval of 25 to 1000° C. of not more than 40×10⁻⁷° C.⁻¹ asmeasured by dilatometry. Previous zirconium tin titanate bodies reportedin the prior art exhibit a CTE (25-1000° C.) of more than 45×10⁻⁷° C.⁻¹.The lower CTE values of the exemplary bodies of the present disclosurecan be achieved by selecting a composition wherein the zirconium tintitanate phase contains not more than 30 mol % TiO₂ and selecting acombination of raw materials and a firing temperature and time thatenable sufficient grain growth to cause microcracking. Predominant asused herein refers to more than 50 wt % of the ceramic body.Microcracked, low-titanium zirconium tin titanate bodies have not beenknown prior to the present disclosure.

An exemplary embodiment of the present disclosure relates to amicrocracked ceramic body comprising a predominant phase of zirconiumtin titanate and having a coefficient of thermal expansion (25-1000° C.)of not more than about 40×10⁻⁷° C.⁻¹ as measured by dilatometry. Inpreferred embodiments, the dilatometric CTE from 25 to 1000° C. of theexemplary microcracked ceramic bodies is not more than 35×10⁻⁷° C.⁻¹,not more than 30×10⁻⁷° C.⁻¹, and even not more than 25×10⁻⁷° C.⁻¹. Whenthe microcracked ceramic body has a honeycomb structure, the coefficientof thermal expansion is measured parallel to the length of the channelson a bar cut from the ceramic body. The zirconium tin titanate phase isa phase having a crystal structure based upon one or more of the crystalstructures displayed by the compound ZrTiO₄ and containing tin inaddition to titanium and zirconium.

In certain preferred embodiments, the composition of the zirconium tintitanate phase of the ceramic body fulfills the requirement that40≤Z≤65, 13≤S≤50, and 5≤T≤30, where Z=100(mol % ZrO₂)/(mol % ZrO₂+mol %SnO₂+mol % TiO₂), S=100(mol % SnO₂)/(mol % ZrO₂+mol % SnO₂+mol % TiO₂),and T=100(mol % TiO₂)/(mol % ZrO₂+mol % SnO₂+mol % TiO₂), in which themol % (mole percent) of each component is its mole percentage in thezirconium tin titanate phase, and in which the other chemical componentsof the zirconium tin titanate phase, if any, are expressed as the simplemetal oxides (binary compounds of one metal with oxygen). This preferredcompositional range of the zirconium tin titanate phase is depicted inFIG. 2. In other preferred embodiments, the composition of the zirconiumtin titanate phase fulfills the requirement that 40≤Z≤63, 15≤S≤45, and5≤T≤27, as shown in FIG. 3. In especially preferred embodiments, thecomposition of the zirconium tin titanate phase fulfills the requirementthat 45≤Z≤63, 15≤S≤43, and 7≤T≤25, as shown in FIG. 4.

In some of these exemplary embodiments the predominant phase ofzirconium tin titanate phase is at least 60 wt % of the ceramic body.For example, the zirconium tin titanate phase is at least 70 wt % of theceramic body. For example, the zirconium tin titanate phase is at least80 wt % of the ceramic body. For example, the zirconium tin titanatephase is at least 90 wt % of the ceramic body. For example, thezirconium tin titanate phase is at least 95 wt % of the ceramic body.For example, the zirconium tin titanate phase is even at least 99 wt %of the ceramic body.

The zirconium tin titanate phase may also contain minor amounts of othersubstituents such as Hf, Al, Ga, Fe, Cr, Mn, Ta, Nb, In, and Sb,preferably not to exceed 5 cation percent and more preferably not toexceed 1 cation percent of the zirconium tin titanate phase. Otherphases may be present in the body, such as one or more of a zirconiumoxide based phase and a tin oxide based phase. The zirconium oxide basedphase can include titanium and tin in solid solution and may optionallyinclude minor amounts of other substituents such as Ce, Y, Ca, Mg, Fe,Hf, etc., and can be a monoclinic baddeleyite-type phase at roomtemperature (RT), which is about 25° C. Where a baddeleyite-type phaseis present, it preferably undergoes a transformation to a tetragonalcrystal structure at a temperature of less than 1000° C. during heating.The tin oxide based phase can include titanium and zirconium in solidsolution and may contain minor amounts of other substituents such as Fe,Ta, Nb, Zn, W, Mn, Sc, Ge, In, Ga, etc.

The atomic crystal lattice of the zirconium tin titanate phase is basedupon that of α-PbO₂ and belongs to the space group Pbcn. The symmetry isorthorhombic with a unit cell having an a axis, b axis, and c axisorthogonal to one another. Each of these three unit cell parametersexhibits a different coefficient of thermal expansion from one another,CTE(a), CTE(b), and CTE(c), which are referred to as the lattice axialCTE values or simply axial CTE values. These lattice axial CTE valuesvary with the composition of the zirconium tin titanate compound. Theaverage of the three axial CTE values is referred to as the mean latticeaxial CTE or mean lattice CTE. The lowest axial CTE value for azirconium tin titanate compound of a given composition is referred to asthe minimum axial CTE value, CTE_(min), and can be found to be theb-axis CTE, CTE(b). The highest axial CTE value for a zirconium tintitanate compound of a given composition is referred to as the maximumaxial CTE value, CTE_(max), and can be found to be the a-axis CTE,CTE(a). The difference between the highest and lowest axial CTE valuesfor a given zirconium tin titanate compound is referred to as themaximum lattice CTE anisotropy, or simply the CTE anisotropy, of thephase, ΔCTE_(max). The lattice axial CTE values of the zirconium tintitanate phase are determined by measuring the dimensions of the threeunit cell parameters over a series of temperatures by high-temperaturex-ray diffractometry, and the CTE values are defined here as the mean(“secant”) CTE values from 25 to 1000° C.

In exemplary embodiments of the present disclosure, the lowest crystallattice axial CTE value of the zirconium tin titanate phase, CTE_(min),must be not greater than 30×10⁻⁷° C.⁻¹, for example, is not greater than20×10⁻⁷° C.⁻¹, not greater than 10×10⁻⁷° C.⁻¹, not greater than 0×10⁻⁷°C.⁻¹, not greater than −10×10⁻⁷° C.⁻¹, and even not greater than−20×10⁻⁷° C.⁻¹. The crystal lattice CTE anisotropy of the zirconium tintitanate phase is preferably at least 60×10⁻⁷° C.⁻¹, and more preferablyat least 80×10⁻⁷° C.⁻¹, for example, at least 100×10⁻⁷° C.⁻¹, at least110×10⁻⁷° C.⁻¹, at least 120×10⁻⁷° C.⁻¹, at least 130×10⁻⁷° C.⁻¹, andeven at least 140×10⁻⁷° C.⁻¹. It is found that lattice axial CTE valuesfor zirconium tin titanate compounds naturally vary with composition insuch a way that the minimum axial CTE value tends to decrease as thelattice axial CTE anisotropy increases.

A ceramic body comprising very fine grains of a zirconium tin titanatephase can have a bulk CTE, as measured by dilatometry, that is equal to,or nearly equal to, the mean lattice axial CTE of the zirconium tintitanate phase. However, when the CTE anisotropy of the zirconium tintitanate phase is high, stresses will develop between adjacent grainshaving different crystallographic orientations within the microstructureduring cooling of the ceramic after firing. For a CTE anisotropy of agiven magnitude, if the grain size of the zirconium tin titanate phaseis sufficiently large, these stresses result in the formation ofmicrocracks throughout the ceramic body. The microcracks tend to formgenerally orthogonal to the directions of highest lattice axial CTEbecause these directions undergo the greatest contraction during coolingand thereby develop the highest tensional stresses. As a result of themicrocracking, the highest axial CTE directions in the adjacentzirconium tin titanate grains are no longer in contact with one another.Consequently, during reheating of the ceramic, the microcracks serve as“expansion joints” whereby the expansion of the zirconium tin titanategrains along the direction of the highest axial CTE is accommodated by are-closing of the microcracks. By this mechanism, the bulk CTE of theceramic, as measured by dilatometry, is reduced to a value that is lessthan the mean lattice axial CTE. With progressively greatermicrocracking and the resulting “decoupling” of the highest, and eventhe second-highest, axial CTE values from the bulk CTE, the coefficientof thermal expansion of the ceramic body approaches the value of theminimum axial CTE value, CTE_(min). Accordingly, in order to achieve adilatometric CTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹ in the zirconium tintitanate-containing ceramic, the minimum lattice axial CTE must be notmore than 30×10⁻⁷° C.⁻¹ and the ceramic body must be microcracked so asto reduce the dilatometric CTE of the bulk ceramic to 40×10⁻⁷° C.⁻¹.Microcracked bodies comprising a predominant zirconium tin titanatephase having a CTE_(min) 30×10⁻⁷° C.⁻¹ have not been previouslydisclosed.

The extent of microcracking may be quantified by either of two methodsas disclosed herein. In accordance with one method, the “microcrackindex,” also referred to as “microcrack density,” may be determined bystereological analysis of a scanning electron microscopy image of apolished cross section of the ceramic. The magnification of the image isselected such that the microcrack traces are clearly visible while stillimaging as many microcracks in the field of view as is practical. In thefirst step of the analysis, the microcrack traces are identified andtheir number is counted over the entire area of the micrograph, yieldingthe value n. Either an array of parallel lines or a set of at leastthree concentric circles is then superimposed on the SEM image of themicrostructure and the points at which the lines or circles intersectthe microcrack traces are identified and counted to yield the value p.The total of the lengths of all of the lines in the array (length of oneline multiplied by the number of lines drawn on the image), or the totallength of the sum of the circumferences of the circles, is thencalculated as the value L in units of μm (microns). The number ofintercept points per unit length, P_(L), is calculated as the value ofp/L in units of μm⁻¹. From stereological principles, the total lengthsof the 2D microcrack traces per unit area of the SEM image is computedas L_(A)=(π/2)P_(L) in units of μm/μm² (or μm⁻¹). The mean length of theindividual 2D microcrack traces is then calculated as

l

=L_(A)(A/n) where A is the area of the entire micrograph image overwhich n was counted, in units of μm². The value of

l

is in units of μm. The value of

l

is then divided by two to obtain the mean 2D microcrack tracehalf-length,

l

/2, and this value is then multiplied by 4/π to obtain the mean 3Dmicrocrack half-length, b=(4/π)

l

/2 in units of μm. This value of b is equated to the radius of adisc-shaped microcrack. Finally, the total number of microcracks perunit volume (that is, in 3D), is defined as N=(2n/A)/(πb) in units ofcracks/μm³. After substituting terms and simplifying the form of theequation, the value of the microcrack index, or microcrack density,(Nb³)_(IA), where the subscript “IA” indicates derivation of the Nb³value from image analysis, can then be computed according to thefollowing Equation 1:(Nb ³)_(IA)=2(P _(L))²/(πn/A)  (Eq 1)

For accuracy, when the sample contains more than about 10% porosity, thetotal area over which the crack traces are counted and the total lengthof all the lines or circumferences over which the number ofintersections with crack traces are counted should be reduced by thefraction of porosity contained within the count area or intercepted bythe lines or circles.

The second method for assessing the microcrack density is based uponmeasurement of the Young's elastic modulus of the ceramic body from roomtemperature to 1200° C. and back to room temperature again. Duringheating, the microcracks in the ceramic gradually close. As the opposingsurfaces of each crack come into contact and, at high temperatures,anneal shut, the resulting stiffening of the body is manifested by anincrease in the elastic modulus. During cooling, there can be atemperature interval over which the elastic modulus undergoes a small,linear increase with decreasing temperature before the microcracksreopen at lower temperature, whereupon the elastic modulus decreasestoward its initial, pre-heated value. Extrapolation of a tangent line tothis linear portion of the cooling curve to 25° C. establishes the valueof the elastic modulus of the sample at room temperature in ahypothetically non-microcracked state. This extrapolated value isdesignated E°₂₅. By applying the theoretical model of Budiansky andO'Connell (Budiansky, B. and O'Connell, R. J. (1976) Elastic moduli of acracked solid, Int. J. Solids Structures, 12, 81-97), the microcrackdensity, (Nb³)_(EM), where the subscript “EM” indicates derivation fromthe elastic modulus measurements, can be estimated from the ratio of theelastic modulus of the microcracked sample measured at room temperaturebefore heating, E₂₅, to the value E°₂₅ extrapolated from the linearportion of the E vs. T cooling curve, via the following Equation 2:(Nb ³)_(EM)=(9/16)[1−(E ₂₅ /E° ₂₅)]  (Eq 2)

The extent of microcracking that is required to achieve a dilatometricCTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹ when the mean lattice CTE_(25-1000° C.)is >40×10⁻⁷° C.⁻¹ is related to the minimum lattice axial CTE.Specifically, the amount of microcracking required to achieve adilatometric CTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹ is greater for compositionswith high values of CTE_(min) nearer to 30×10⁻⁷° C.⁻¹. Zirconium tintitanate compositions with very low values of CTE_(min) require lessmicrocracking to achieve a dilatometric CTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹,although microcracking is still required.

In exemplary embodiments of the disclosure, the microcrack density ofthe ceramic body as determined by at least one of the above two methodsfulfills the following Equation 3:Nb ³ ≥k₁[0.102+6.00×10⁴(CTE_(min))+1.23×10¹⁰(CTE_(min))²+8.38×10¹⁴(CTE_(min))³]  (Eq3)

Where k₁ is ≥1.0. In preferred exemplary embodiments, k₁ is at least1.5, at least 2.0, at least 2.5, and even at least 3.0. The lower limitfor Nb³ defined by Equation 3 (Eq 3) for k₁=1.0 is plotted against thevalue of CTE_(min) in FIG. 5. Thus, for example, if the value ofCTE_(min) for the zirconium tin titanate phase in a given exemplaryceramic body is 10×10⁻⁷° C.⁻¹, then the microcrack index required toachieve a dilatometric CTE of less than 40×10⁻⁷° C.⁻¹ must be at least0.175. Also plotted in FIG. 5 are other preferred lower limits for Nb³corresponding to values of k₁=1.5, 2.0, 2.5, and 3.0.

The extent of microcracking that occurs within the zirconium tintitanate ceramic is proportional to the maximum lattice CTE anisotropyand the grain size of the ceramic. For a given grain size, a change inthe composition of the zirconium tin titanate phase that results in ahigher CTE anisotropy will result in more microcracking and a highervalue of Nb³. Likewise, for a zirconium tin titanate ceramic of a givencomposition and CTE anisotropy, a larger grain size will result in moremicrocracking and a lower dilatometric CTE.

The grain size parameter, g, of the zirconium tin titanate phase isdetermined by a line intercept method applied to an optical or scanningelectron microscopy image of a polished section of the ceramic in whichthe grains are distinguishable from one another, and represents theaverage of the widths of the grains measured at random positions acrossthe grains in the two-dimensional image. For example, the grain sizeparameter may be measured according to the “Abrams Three-CircleProcedure” as described in ASTM E112-13. The term “grain size parameter”herein refers to the average intercept length of the grains on thetwo-dimensional polished section. In practice, the value of g iscalculated from the relation in the following Equation 4:g=L/p  (Eq 4)

Where p is the number of intercepts between the grain boundaries and anarray of lines of total length L or between the grain boundaries and oneor more circles whose circumferences total to a length L, where L is inunits of micrometers. In practice, it is preferred that themagnification of the optical or scanning electron microscopy image andthe number of lines or circles drawn on that image are selected so as toyield a value of L/g of at least 25, and more preferably at least 50, inorder to provide adequate counting statistics for calculation of thegrain size parameter.

In accordance with an exemplary embodiment of the disclosure, it hasbeen determined that the minimum value of the grain size parameter (inunits of microns), required to provide sufficient microcracking to yielda CTE<40×10⁻⁷° C.⁻¹ is related to the minimum lattice axial CTE (inunits of ° C.⁻¹) according to the following Equation 5:g≥k₂[4.15+1.99×10⁶(CTE_(min))+3.58×10¹¹(CTE_(min))²+2.15×10¹⁶(CTE_(min))³]  (Eq 5)

Where k₂ is ≥1.0. In embodiments, k₂ is at least 1.25, for example, atleast 1.50, at least 1.75, and even at least 2.00. The lower limit forthe preferred values of g calculated from Eq. 5 (k₂=1.0) is plottedagainst the value of CTE_(min) in FIG. 6. Thus, for example, if thevalue of CTE_(min) for the zirconium tin titanate phase in a givenexemplary ceramic body is 10×10⁻⁷° C.⁻¹, then the grain size required toachieve a dilatometric CTE of less than 40×10⁻⁷° C.⁻¹ must be at least6.5 μm. Also plotted in FIG. 6 are other preferred lower limits for gcorresponding to values of k₂=1.25, 1.50, 1.75, and 2.00.

As mentioned, a zirconium tin titanate ceramic having a dilatometricCTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹ has not been disclosed previously. Inaddition, no example of a zirconium tin titanate ceramic has beendisclosed previously possessing a combination of composition andmicrostructure that would inherently possess a bulk CTE of ≤40×10⁻⁷°C.⁻¹ even if the CTE of the body was not reported. Previous studies haveusually been directed to the formation of zirconium tin titanateceramics for dielectric applications, where the CTE of the body is notimportant and where microcracking would have undesirable effects on thedielectric properties, particularly in the presence of moisture.Furthermore, such studies have tended to focus on compositions in whichTiO₂ comprised more than 30 mol % of the ceramic, for whichCTE_(min)>30×10⁻⁷° C.⁻¹ in the zirconium tin titanate phase and forwhich a dilatometric CTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹ could not have beenachieved even with microcracking present.

Hirano et al. (Hirano, S., Hayashi, T., and Hattori, A. (1991) “ChemicalProcessing and Microwave Characteristics of (Zr,Sn)TiO₄ MicrowaveDielectrics,” J. Am. Cer. Soc. 74 [6] 1320-1324) prepared a solution ofzirconium, tin, and titanium isopropoxides which was subsequentlyhydrolyzed to produce a precipitation of amorphous powder ofZr_(0.8)Sn_(0.2)TiO₄ composition by several processing routes. Medianparticle sizes were 0.4 μm or finer. Powders were pressed into discsthat were fired at 1600° C. for 3 or 24 hours. The microstructurecomprised densely packed grains with no evidence of microcracking. Grainsize measured by the present investigation on Hirano's electronmicroscopy image for the sample that was held for 24 hours at 1600° C.using the three-circle intercept method yielded a grain size of 9.4microns. The composition of Hirano's zirconium tin titanate phase wouldinherently have a mean lattice CTE_(25-1000° C.) of about 74×10⁻⁷° C.⁻¹and a minimum axial CTE of about 58×10⁻⁷° C.⁻¹. In the absence ofmicrocracks, Hirano's ceramic would have a dilatometric CTE of about74×10⁻⁷° C.⁻¹.

Huang and Weng (Huang, C.-L. and Weng, M.-H. (2000) “Liquid phasesintering of (Zr,Sn)TiO₄ microwave dielectric ceramics,” Mat. Res.Bull., 35, 1881-1888) sintered Zr_(0.8)Sn_(0.2)TiO₄ ceramics at 1220 and1300° C. with 0.5, 1.0, and 2.0 wt % copper oxide additions as sinteringaids. Microstructures exhibited densely packed grains with no evidenceof microcracking. The composition of Huang and Weng's zirconium tintitanate phase would inherently have a mean lattice CTE_(25-1000° C.) ofabout 74×10⁻⁷° C.⁻¹ and a minimum lattice axial CTE of about 58×10⁻⁷°C.⁻¹. In the absence of microcracks, the ceramic of Huang and Weng wouldhave a dilatometric CTE of about 74×10⁻⁷° C.⁻¹.

Huang et al. (Huang, C.-L., Weng, M.-H., Chen, H.-L. (2001) “Effects ofadditives on microstructures and microwave dielectric properties of(Zr,Sn)TiO₄ ceramics,” Materials Chemistry and Physics 71, 17-22)subsequently prepared sintered Zr_(0.8)Sn_(0.2)TiO₄ ceramics at 1300° C.with 1.0 wt % bismuth oxide or 1.0 wt % vanadium pentoxide additions assintering aids. Microstructures again comprised densely packed grainswith no evidence of microcracking. The composition of Huang's zirconiumtin titanate phase would inherently have a mean latticeCTE_(25-1000° C.) of about 74×10⁻⁷° C.⁻¹ and a minimum lattice axial CTEof about 58×10⁻⁷° C.⁻¹. In the absence of microcracks, Huang's ceramicwould have a dilatometric CTE of about 74×10⁻⁷° C.⁻¹.

Houivet et al. (Houivet, D., El Fallah, J., Lamagnere, B., Haussonne,J.-M. (2001) Effect of annealing on the microwave properties of(Zr,Sn)TiO₄ ceramics, J. Eur. Cer. Soc., 21, 1727-1730) prepared aZr_(0.65)Sn_(0.33)Ti_(1.02)O₄ ceramic from metal oxide powders ofunspecified particle size, with additions of lanthanum and nickel oxidesas sintering aids, and fired the compact thereof at 1370° C. for 20hours. Houivet's micrograph of an as-fired surface shows a grain size of“30 to 50 μm” for the zirconium tin titanate phase and no evidence ofmicrocracking. The composition of Houivet's zirconium tin titanate phasewould inherently have a mean lattice CTE_(25-1000° C.) of about 70×10⁻⁷°C.⁻¹ and a minimum lattice axial CTE of about 50×10⁻⁷° C.⁻¹. In theabsence of microcracks, Houivet's ceramic would have a dilatometric CTEof about 70×10⁻⁷° C.⁻¹.

Iddles et al. (Iddles, D. M., Bell, A. J., Moulson, A. J. (1992)Relationships between dopants, microstructure and the microwavedielectric properties of ZrO₂—TiO₂—SnO₂ ceramics, J. Mater. Sci, 27,6303-6310) prepared Zr_(0.875)Ti_(0.875)Sn_(0.25)O₄ ceramics from amixture of the metal oxide powders of unspecified particle size byfiring at 1325-1375° C. for up to 128 hours. Micrographs show noevidence of microcracking. The composition of Iddles' zirconium tintitanate phase would inherently have a mean lattice CTE_(25-1000° C.) ofabout 70×10⁻⁷° C.⁻¹ and a minimum lattice axial CTE of about 50×10⁻⁷°C.⁻¹. In the absence of microcracks, Iddles' ceramic would have adilatometric CTE of about 70×10⁻⁷° C.⁻¹.

Kim et al. (Kim, D.-J., Hahn, J.-W., Han, G.-P., Lee, S.-S., Choy, T.-G.(2000) Effects of Alkaline-Earth-Metal Addition on the Sinterability andMicrowave Characteristics of (Zr,Sn)TiO₄ Dielectrics) preparedZr_(0.8)Sn_(0.2)TiO₄ ceramics from pressed discs of mixtures of metaloxide powders of unspecified particle size with and without sinteringaids and fired these at 1300-1625° C. Optical micrographs showed noevidence of microcracking. The composition of Kim's zirconium tintitanate phase would inherently have a mean lattice CTE_(25-1000° C.) ofabout 74×10⁻⁷° C.⁻¹ and a minimum lattice axial CTE of about 58×10⁻⁷°C.⁻¹. In the absence of microcracks, Kim's ceramic would have adilatometric CTE of about 74×10⁻⁷° C.⁻¹.

In sum, a Zr—Sn-titanate ceramic that could have exhibited aCTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹ was not previously known or suggested inthe art.

Exemplary embodiments of the present disclosure also provide a method ofmanufacturing zirconium tin titanate ceramic articles from a ceramicforming precursor batch composition comprised of certain inorganicpowdered raw materials. Generally, the method first comprises providingan inorganic batch composition comprising a zirconium containing source,a titanium containing source, and a tin containing source. The inorganicbatch composition is then mixed together with one or more processingaid(s) selected from the group consisting of a plasticizer, lubricant,binder, pore former, and solvent, to form a plasticized ceramicprecursor batch composition. The inorganic powdered raw materials of theinorganic batch composition may be mixed or may be not mixed prior tomixing together with the one or more processing aid(s). The plasticizedceramic precursor batch composition can be shaped or otherwise formedinto a green body, optionally dried, and subsequently fired underconditions effective to convert the green body into a ceramic article.

The zirconium containing source can, for example and without limitation,be provided as ZrO₂ powder

The titanium containing source can be provided as TiO₂ powder.

The tin containing source can be provided as SnO₂ powder.

Minor amounts of other constituents can be added to the precursor batchcomposition or be included in the zirconium containing source, titaniumcontaining source, and the tin containing source. For example, Hf, Al,Si, Ga, Fe, Cr, Mn, Ta, Nb, In, Sb, La, Ce, Y, Sr, Ca, Mg, Zn, W, Sc,and Ge can be added to the precursor batch composition. For example,these other constituents may be present or can be added to the precursorbatch composition to lower the firing temperature and broaden the firingwindow required to form the ceramic composition. The amount of theseother constituents can, for example, be from 0 to 10 weight percent ofthe total composition. For example, these other constituents may bepresent or can be added in an amount of between about 0.1 and 3.0 wt %,for example, between about 0.25 and 2.0 wt %.

Still further, the ceramic precursor batch composition may compriseother additives such as surfactants, oil lubricants and pore-formingmaterial. Non-limiting examples of surfactants that may be used asforming aids are C₈ to C₂₂ fatty acids, and/or their derivatives.Additional surfactant components that may be used with these fatty acidsare C₈ to C₂₂ fatty esters, C₈ to C₂₂ fatty alcohols, and combinationsof these. Exemplary surfactants are stearic, lauric, myristic, oleic,linoleic, palmitic acids, and their derivatives, tall oil, stearic acidin combination with ammonium lauryl sulfate, and combinations of all ofthese. In an illustrative embodiment, the surfactant is lauric acid,stearic acid, oleic acid, tall oil, and combinations of these. In someof these embodiments, the amount of surfactants is from about 0.25% byweight to about 2% by weight.

Non-limiting examples of oil lubricants used as forming aids includelight mineral oil, corn oil, high molecular weight polybutenes, polyolesters, a blend of light mineral oil and wax emulsion, a blend ofparaffin wax in corn oil, and combinations of these. In someembodiments, the amount of oil lubricants is from about 1% by weight toabout 10% by weight. In an exemplary embodiment, the oil lubricants arepresent from about 3% by weight to about 6% by weight.

The precursor composition can, if desired, contain a pore-forming agentto tailor the porosity and pore size distribution in the fired body fora particular application. A pore former is a fugitive material whichevaporates or undergoes vaporization by combustion during drying orheating of the green body to obtain a desired, usually higher porosityand/or coarser median pore diameter. A suitable pore former can include,without limitation, carbon; graphite; starch; wood, shell, or nut flour;polymers such as polyethylene beads; waxes; and the like. When used, aparticulate pore former can have a median particle diameter in the rangeof from 10 μm to 70 μm, and more preferably from 15 μm to 50 μm.

The inorganic ceramic forming batch components, along with any optionalsintering aid and/or pore former, can be intimately blended with aliquid vehicle and forming aids which impart plastic formability andgreen strength to the raw materials when they are shaped into a body.When forming is done by extrusion, a cellulose ether binder such asmethylcellulose, hydroxypropyl methylcellulose, methylcellulosederivatives, and/or any combinations thereof, can serve as a temporaryorganic binder, and sodium stearate can serve as a lubricant. Therelative amounts of forming aids can vary depending on factors such asthe nature and amounts of raw materials used, etc. For example, thetypical amounts of forming aids are about 2% to about 10% by weight ofmethyl cellulose, and preferably about 3% to about 6% by weight, andabout 0.5% to about 1% by weight sodium stearate, stearic acid, oleicacid or tall oil, and preferably about 0.6% by weight. The raw materialsand the forming aids are typically mixed together in dry form and thenmixed with water as the vehicle. The amount of water can vary from onebatch of materials to another and therefore is determined by pre-testingthe particular batch for extrudability.

The liquid vehicle component can vary depending on the type of materialused in order to impart optimum handling properties and compatibilitywith the other components in the ceramic batch mixture. The liquidvehicle content can be in the range of from 15% to 50% by weight of theplasticized composition. In one embodiment, the liquid vehicle componentcan comprise water. In another embodiment, depending on the componentparts of the ceramic batch composition, it should be understood thatorganic solvents such as, for example, methanol, ethanol, or a mixturethereof can be used as the liquid vehicle.

Forming or shaping of the green body from the plasticized precursorcomposition may be done by, for example, typical ceramic fabricationtechniques, such as uniaxial or isostatic pressing, extrusion, slipcasting, and injection molding. Extrusion is preferred when the ceramicarticle is of a honeycomb geometry, such as for a catalytic converterflow-through substrate or a diesel particulate wall-flow filter. Theresulting green bodies can be optionally dried, and then fired in a gasor electric kiln or by microwave heating, under conditions effective toconvert the green body into a ceramic article. For example, the firingconditions effective to convert the green body into a ceramic articlecan comprise heating the green body at a maximum soak temperature in therange of from 1350° C. to 1750° C., for example, in the range of from1400° C. to 1700° C., or in the range of from 1450° C. to 1650° C., andmaintaining the maximum soak temperature for a hold time sufficient toconvert the green body into a ceramic article, followed by cooling at arate sufficient not to thermally shock the sintered article. Forexample, compositions in which the composition of the zirconium tintitanate phase satisfies the relation 15≤S≤32 and 5≤T≤22 may be fired atthe lower end of the firing range.

To obtain a wall-flow filter, a portion of the cells of the honeycombstructure at the inlet end or face are plugged. The plugging is only atthe ends of the cells which can be to a depth of about 1 to 20 mm,although this can vary. A portion of the cells on the outlet end but notcorresponding to those on the inlet end are plugged. Therefore, eachcell is plugged only at one end. An exemplary arrangement is to haveevery other cell on a given face plugged in a checkered pattern.Alternatively, when a portion of the cells are not plugged at both theinlet end and the outlet end, a partial filter is obtained. Further, aportion of the cells can be plugged at both the inlet and outlet ends toprovide thermal and/or filtration variability to the substrate, filter,or partial filter.

EXAMPLES

Exemplary embodiments of the disclosure are further described below withrespect to certain exemplary and specific embodiments thereof, which areillustrative only and not intended to be limiting. Exemplary andcomparative experimental examples were prepared to further illustrateand to provide a further understanding of the disclosure and areincorporated in and constitute a part of this specification, andtogether with the description serve to further explain the principles ofthe disclosure.

In accordance with some of the embodiments, eleven ceramic compositionsin the ZrO₂—TiO₂—SnO₂ system as provided in Table 1 were prepared frommixtures of the component metal oxide powders. Raw materials comprisedzirconium oxide (median particle diameter=6 μm), titanium oxide (medianparticle diameter=0.4 μm), and tin oxide (median particle diameter=6μm). Particle sizes were measured by laser diffraction using a MicrotracS3500 particle size analyzer. Batches comprising 1500 grams of theoxides were weighed out and mixed with 135 grams of methyl cellulose asa binder in a Processall® Mixer. The batch was transferred to astainless steel muller and plasticized with either 225 ml of deionizedwater (compositions D to I) or 150 ml deionized water and 15 grams oftall oil (compositions L to Q). The material was transferred to a ramextruder, vacuum was pulled on the mixture, and the material was passedthrough a “spaghetti die” several times before being extruded as 8 mmdiameter rod. The rod was cut into 24-inch sections that were placed inglass tubes and dried in a convection oven for several days. Dried rodswere cut into segments that were set in an alumina tray and fired in anelectric furnace at 50° C./h to 1400, 1500, or 1600° C., held for 10hours, and cooled at a nominal rate of 500° C./h. Cooling rate wasslower at lower temperatures due to the thermal mass of the furnace.Portions of the rods were crushed and submitted for x-ray diffractometrywith Rietveld refinement of the data. Other rods were used formeasurement of CTE by dilatometry. Porosities of compositions sinteredat 1400° C. were determined from their theoretical densities and theArchimedes method. Additional samples of four of the eleven compositionswere fired at 1600° C. for measurement of mercury porosimetry,four-point modulus of rupture, and Young's elastic modulus to 1200° C.(sonic resonance technique).

TABLE 1 Batch compositions of examples Composition Code D E F G H L M NO P Q Wt % ZrO₂ 60.67 54.93 50.17 44.02 40.59 48.77 47.44 46.18 65.4561.59 58.15 Wt % TiO₂ 39.33 24.92 13.01 38.04 26.31 9.48 6.15 2.99 21.2113.31 6.28 Wt % SnO₂ 0.00 20.15 36.82 17.94 33.10 41.75 46.41 50.8313.34 25.11 35.56 Mole % ZrO₂ 50.0 50.0 50.0 37.5 37.5 50.0 50.0 50.060.0 60.0 60.0 Mole % TiO₂ 50.0 35.0 20.0 50.0 37.5 15.0 10.0 5.0 30.020.0 10.0 Mole % SnO₂ 0.0 15.0 30.0 12.5 25.0 35.0 40.0 45.0 10.0 20.030.0 Nominal Zr per 4 1.00 1.00 1.00 0.75 0.75 1.00 1.00 1.00 1.20 1.201.20 Stoichiometry oxygens of Zirconium Ti per 4 1.00 0.70 0.40 1.000.75 0.30 0.20 0.10 0.60 0.40 0.20 Tin Titanate oxygens Phase Sn per 40.00 0.30 0.60 0.25 0.50 0.70 0.80 0.90 0.20 0.40 0.60 oxygens

The unit cell parameters of the zirconium tin titanate phases sinteredat 1600° C. (Table 5), as derived by Rietveld refinement of the XRDpatterns, were fit as a function of the nominal compositions of thezirconium tin titanate phases. The variables available to the model foreach unit cell parameter were N_(Zr), N_(Sn), N_(Ti), and the squares ofthese variables, where N_(i) is the number of atoms of element “i” in a4-oxygen formula unit. Only those variables with a statisticallysignificant correlation were included in each model. Data for all tensamples were used for fitting each parameter with the exception of the aparameter, in which the P6 and Q6 examples were identified as beingstatistical outliers. The corresponding equations are as follows, forwhich the R² values were at least 99.5%:

$\begin{matrix}{{a\text{-}{dimension}\mspace{14mu}(Å)} = {4.54656 + {0.260861\left( N_{Zr} \right)} + {0.0657063\left( N_{Sn} \right)}}} & \left( {{Eq}\mspace{14mu} 6} \right) \\{{b\text{-}{dimension}\mspace{14mu}(Å)} = {5.07079 + {0.707332\left( N_{Sn} \right)} - {0.321695\left( N_{Sn} \right)^{2}} + {0.21806\left( N_{Zr} \right)} + {0.13948\left( N_{Ti} \right)^{2}}}} & \left( {{Eq}\mspace{14mu} 7} \right) \\{{c\text{-}{dimension}\mspace{14mu}(Å)} = {5.25636 - {0.182123\left( N_{Ti} \right)} - {0.0489722\left( N_{Zr} \right)}}} & \left( {{Eq}\mspace{14mu} 8} \right)\end{matrix}$

Equations (6), (7), and (8) were used to back-calculate the compositionsof the zirconium tin titanate phases at 1400° C., 1500° C., and 1600° C.for those examples for which the unit cell parameters were determined.All zirconium tin titanate phases were found to be within about ±2atomic percent of their nominal compositions with the exception of theN, P and Q compositions. The zirconium tin titanate phase in the Ncomposition was found to be enriched in zirconium and depleted in tinrelative to the nominal batched composition, and the sample alsocontained substantial tin oxide solid solution and minor zirconium oxidesolid solution as second phases (Table 3). This implies that the bulkcomposition of N lies somewhat outside the stability limit of thezirconium tin titanate field at 1500° C., lying within the zirconium tintitanate+tin oxide solid solution+zirconium oxide solid solutionthree-phase region, close to the zirconium tin titanate+tin oxide solidsolution two-phase tie line. The zirconium tin titanate phases in the Pand Q compositions were found to be depleted in zirconium and enrichedin tin (and to a lesser extent enriched in titanium) as shown in Tables3, 4, and 5. This suggests that the bulk P and Q compositions lieslightly outside the stability limits of the zirconium tin titanatephase field, and within the zirconium tin titanate+zirconium oxide solidsolution two-phase region.

Also determined were the lattice axial CTE values for the tencompositions fired at 1600° C. using high-temperature x-raydiffractometry, in which the unit cell parameters were measured at 100°C. intervals to 1000° C. Values of CTE(a), CTE(b), CTE(c), mean latticeCTE, and maximum CTE anisotropy are reported in Table 6.

Only the first five compositions, D to H, were sintered at 1400° C., andall examples are comparative (Table 2). Compositions of examples D4, E4,G4, and H4 lie outside the composition range of the exemplaryembodiments of the present disclosure and cannot achieve a dilatometricCTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹ because their minimum lattice axial CTEis >30×10⁻⁷° C.⁻¹ and therefore no physically realistic level ofmicrocracking would be capable of reducing the CTE_(25-1000° C.) of aceramic body of those compositions to the range of less than 40×10⁻⁷°C.⁻¹. The composition of example F4 does lie within the compositionalrange of the exemplary embodiments, and the minimum axial CTE value ofthe zirconium tin titanate phase is less than 30×10⁻⁷° C.⁻¹ andtherefore lies within the range of the exemplary embodiments for theseparameters; however, the microcrack index (Nb³)_(IA) value of 0.010 andthe grain size of 2.8 μm lie outside the ranges of the exemplaryembodiments of the present disclosure (FIGS. 5 and 6). The small grainsize of the F composition sintered at 1400° C. is insufficient topromote the amount of microcracking required to reduce the CTE of theceramic to ≤40×10⁻⁷° C.⁻¹. It is also evident that the addition of tinreduces the grain size of the ceramic body from 8.2 μm for example D4 to2.8 μm for example F4.

TABLE 2 Properties of comparative examples fired at 1400° C. ExampleCode D4 E4 F4 G4 H4 Example Type Comp Comp Comp Comp Comp CompositionCode D E F G H Nominal Composition Zr per 4 ox 1.00 1.00 1.00 0.75 0.75Ti per 4 ox 1.00 0.70 0.40 1.00 0.75 Sn per 4 ox 0.00 0.30 0.60 0.250.50 Composition Derived from Lattice Parameters Zr per 4 ox 1.01 1.000.99 0.74 0.76 Ti per 4 ox 0.98 0.69 0.40 1.01 0.77 Sn per 4 ox 0.010.31 0.61 0.25 0.47 Weight Percentages by XRD Zirconium Titanate 100 0 00 0 Zirconium Tin Titanate 0 100 99.7 100 99.8 Tin Oxide 0 0 0.3 0 0.2Lattice Parameter a (Å) 4.8085 4.8288 4.8447 4.7548 4.7768 LatticeParameter b (Å) 5.4311 5.5431 5.6195 5.5300 5.5812 Lattice Parameter c(Å) 5.0297 5.0794 5.1347 5.0375 5.0784 Theoretical Density (g cm⁻³)5.135 5.480 5.835 5.264 5.585 Skeletal Density (g cm⁻³) 4.905 4.9795.626 4.840 5.169 Bulk Density (g cm⁻³) 4.785 4.896 4.614 4.789 4.792 %Total Porosity 6.9 10.8 21.6 9.1 14.7 CTE₂₅₋₈₀₀ by dilatometry (10⁻⁷°C.⁻¹) 79.5 58.4 47.1 67.6 59.2 CTE₂₅₋₁₀₀₀ by dilatometry (10⁻⁷° C.⁻¹)81.7 60.8 49.5 70.4 61.4 Mean Lattice CTE₂₅₋₁₀₀₀ (10⁻⁷° C.⁻¹) 86.6 62.449.3 73.5 57.1 Minimum Lattice CTE₂₅₋₁₀₀₀ (10⁻⁷° C.⁻¹) 69.3 37.9 2.458.3 35.9 Maximum CTE Anisotropy (10⁻⁷° C.⁻¹) 34.0 47.6 99.0 27.0 52.3Mean Linear Intercept Grain Size (μm) 8.4 — 2.8 — — Microcrack Index,Nb³ (Image Analysis) 0.059 — 0.010 — —

All eleven compositions were fired at 1500° C. (Table 3). Among these,exemplary examples F5, N5, P5, and Q5 exhibit a dilatometricCTE_(25-1000° C.)≤40×10⁷° C.⁻¹. All four possess compositions within thepreferred range of the exemplary embodiments of the present disclosure(FIG. 7), and all comprise a zirconium tin titanate phase having aminimum lattice axial CTE_(min) 30×10⁻⁷° C.⁻¹. Comparative examples D5,E5, G5, H5, and 05 do not achieve a CTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹.These comparative examples have compositions that lie outside thepreferred range of the exemplary embodiments of the present disclosure(FIG. 7) and their minimum axial CTEs are greater than 30×10⁻⁷° C.⁻¹.Comparative examples L5 and M5 lie within the preferred compositionrange and comprise a zirconium tin titanate phase having a minimumlattice axial CTE_(min) 30×10⁻⁷° C.⁻¹, but do not achieve a dilatometricCTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹. Without wishing to be bound by theory,it is believed that comparative examples L5 and M5 do not achieve adilatometric CTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹ because the grain size ofexamples L5 and M5 lie below the limit required to induce sufficientmicrocracking to reduce the dilatometric CTE to 40×10⁻⁷° C.⁻¹.

TABLE 3 Properties of comparative and exemplary examples fired at 1500°C. Example Code D5 E5 F5 G5 H5 L5 M5 N5 O5 P5 Q5 Example Type Comp CompExem Comp Comp Comp Comp Exem Comp Exem Exem Composition Code D E F G HL M N O P Q Nominal Composition Zr per 4 ox 1.00 1.00 1.00 0.75 0.751.00 1.00 1.00 1.20 1.20 1.20 Ti per 4 ox 1.00 0.70 0.40 1.00 0.75 0.300.20 0.10 0.60 0.40 0.20 Sn per 4 ox 0.00 0.30 0.60 0.25 0.50 0.70 0.800.90 0.20 0.40 0.60 Composition Derived from Lattice Parameters Zr per 4ox 1.01 1.01 0.99 0.74 0.77 1.00 1.04 1.11 1.19 1.16 1.13 Ti per 4 ox0.98 0.68 0.40 0.99 0.75 0.28 0.19 0.11 0.62 0.41 0.22 Sn per 4 ox 0.010.32 0.61 0.26 0.49 0.72 0.77 0.78 0.19 0.43 0.65 Weight Percentages byXRD Zirconium Titanate 100 0 0 0 0 0 0 0 0 0 0 Zirconium Tin Titanate 099.0 95.5 100 100 98.7 91.8 77.6 93.0 96.1 92.6 Tin Oxide 0 0 0 0 0 07.3 19.2 0 0 0 Monoclinic Zirconium 0 1.0 4.5 0 0 1.3 0.9 3.3 6.9 3.87.4 Oxide Lattice Parameter a (Å) 4.8091 4.8306 4.8439 4.7573 4.77924.8539 4.8681 4.8896 4.8699 4.8768 4.8833 Lattice Parameter b (Å) 5.43055.5463 5.6211 5.5331 5.5848 5.6428 5.6557 5.6642 5.5080 5.5923 5.6438Lattice Parameter c (Å) 5.0297 5.0817 5.1347 5.0400 5.0813 5.1555 5.17155.1872 5.0808 5.1271 5.1664 CTE₂₅₋₈₀₀ by 75.7 59.8 34.1 67.4 58.5 43.240.8 39.0 37.7 24.3 37.7 dilatometry (10⁻⁷° C.⁻¹) CTE₂₅₋₁₀₀₀ by 78.162.0 37.5 70.3 60.9 45.4 43.1 39.7 45.0 27.1 37.6 dilatometry (10⁻⁷°C.⁻¹) Mean Lattice 86.6 62.4 49.3 73.5 57.1 47.0 45.1 — 61.2 43.4 40.1CTE₂₅₋₁₀₀₀ (10⁻⁷° C.⁻¹) Minimum Lattice 69.3 37.9 2.4 58.3 35.9 −1.5−7.0 — 38.3 −23.4 −26.5 CTE₂₅₋₁₀₀₀ (10⁻⁷° C.⁻¹) Maximum CTE 34.0 47.699.0 27.0 52.3 105.6 115.2 — 43.6 136.8 143.6 Anisotropy (10⁻⁷° C.⁻¹)

Of the ten compositions fired at 1600° C. (Tables 4 and 5), theexemplary embodiments of the present disclosure examples F6, F6a, L6,M6, M6a, P6, P6a, and Q6 exhibit a dilatometricCTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹. All have compositions that lie withinthe preferred range of the exemplary embodiments of the presentdisclosure (FIG. 8) and all have a minimum lattice axial CTE_(min)30×10⁻⁷° C.⁻¹. Furthermore, the F6a, M6a, and P6a examples all possessgrain sizes and microcrack indices, (Nb³)_(IA), that lie within thepreferred range of the exemplary embodiments of the present disclosure(FIGS. 5 and 6). Without wishing to be bound by theory, it is believedthat the increase in sintering temperature from 1500 to 1600° C.produced a sufficient increase in the grain size of the examples fromthe L and M compositions to provide adequate microcracking and reducethe dilatometric CTE to 40×10⁻⁷° C.⁻¹. Comparative examples D6, D6a, E6,G6, H6, and 06 do not achieve a CTE_(25-1000° C.)≤40×10⁻⁷° C.⁻¹. Thecompositions of these comparative examples lie outside the preferredrange of the exemplary embodiments of the present disclosure (FIG. 7)and their minimum axial CTEs are greater than 30×10⁻⁷° C.⁻¹. Theexamples in Table 5 illustrate the tendency for grain size to decreasewith increasing tin content for a given sintering temperature.

The extent of microcracking in the examples in Table 5 was alsodetermined from measurement of the elastic modulus from room temperatureto 1200° C. as described previously. Plots of E vs. T for examples D6aand M6a are provided in FIGS. 9 and 10, respectively, which illustratethe procedure for deriving the value of E₂₅° required to compute(Nb³)_(EM) from Eq. 2. The microcrack indices, (Nb³)_(EM), determined inthis way also meet the requirements of the exemplary embodiments of thepresent disclosure for which CTE_(min) of the zirconium tin titanatephase is not more than 30×10⁻⁷° C.⁻¹.

TABLE 4 Properties of comparative and exemplary examples fired at 1600°C. (first 1600° C. firing) Example Code D6 E6 F6 G6 H6 L6 M6 O6 P6 Q6Example Type Comp Comp Exem Comp Comp Exem Exem Comp Exem ExemComposition Code D E F G H L M O P Q Nominal Composition Zr per 4 ox1.00 1.00 1.00 0.75 0.75 1.00 1.00 1.20 1.20 1.20 Ti per 4 ox 1.00 0.700.40 1.00 0.75 0.30 0.20 0.60 0.40 0.20 Sn per 4 ox 0.00 0.30 0.60 0.250.50 0.70 0.80 0.20 0.40 0.60 Composition Derived from LatticeParameters Zr per 4 ox 1.00 1.01 0.99 0.74 0.77 0.98 1.01 1.20 1.15 1.13Ti per 4 ox 1.00 0.70 0.40 1.00 0.75 0.30 0.20 0.61 0.41 0.23 Sn per 4ox 0.00 0.30 0.61 0.26 0.48 0.72 0.79 0.19 0.44 0.65 Weight Percentagesby XRD Zirconium Titanate 100 0 0 0 0 0 0 0 0 0 Zirconium Tin Titanate 0100 99.6 100 100 96.6 92.3 94.2 93.7 88.2 Tin Oxide 0 0 0.4 0 0 0 3.9 00.3 0 Monoclinic Zirconium 0 0 0 0 0 3.4 3.8 5.8 6.0 11.8 Oxide LatticeParameter a (Å) 4.8059 4.8290 4.8453 4.7564 4.7787 4.8500 4.8614 4.87454.8750 4.8823 Lattice Parameter b (Å) 5.4287 5.5408 5.6211 5.5321 5.58265.6408 5.6547 5.5076 5.5922 5.6420 Lattice Parameter c (Å) 5.0274 5.07925.1351 5.0392 5.0810 5.1531 5.1694 5.0835 5.1257 5.1646 CTE₂₅₋₈₀₀ by74.6 59.1 26.2 66.8 57.6 26.4 25.5 41.5 16.3 29.7 dilatometry (10⁻⁷°C.⁻¹) CTE₂₅₋₁₀₀₀ by 77.6 61.7 30.2 69.7 60.1 29.8 27.8 48.1 21.7 30.5dilatometry (10⁻⁷° C.⁻¹) Mean Lattice 86.6 62.4 49.3 73.5 57.1 47.0 45.161.2 43.4 40.1 CTE₂₅₋₁₀₀₀ (10⁻⁷° C.⁻¹) Minimum Lattice 69.3 37.9 2.458.3 35.9 −1.5 −7.0 38.3 −23.4 −26.5 CTE₂₅₋₁₀₀₀ (10⁻⁷° C.⁻¹) Maximum CTE34 47.6 99 27 52.3 105.6 115.2 43.6 136.8 143.6 Anisotropy

TABLE 5 Properties of comparative and exemplary examples fired at 1600°C. (second 1600° C. firing) Example Code D6a F6a M6a P6a Example TypeComp Exem Exem Exem Composition Code D F M P Nominal Composition Zr per4 ox 1.00 1.00 1.00 1.20 Ti per 4 ox 1.00 0.40 0.20 0.40 Sn per 4 ox0.00 0.60 0.80 0.40 Composition Derived from Lattice Parameters Zr per 4ox 1.01 0.99 1.02 1.16 Ti per 4 ox 0.98 0.39 0.20 0.41 Sn per 4 ox 0.010.62 0.79 0.44 Weight Percentages by XRD Zirconium Tin Titanate 100.093.7 89.7 90.4 Tin Oxide 0 0 3.4 0 Monoclinic Zirconium Oxide 0 6.3 7.09.6 Lattice Parameter a (Å) 4.8104 4.8445 4.8632 4.8767 LatticeParameter b (Å) 5.4314 5.6231 5.6556 5.5931 Lattice Parameter c (Å)5.0307 5.1360 5.1704 5.1275 % Open Porosity 8.0 9.7 15.9 7.8 Median PoreDiameter (μm) 0.11 0.92 1.90 0.12 CTE₂₂₋₈₀₀ by dilatometry (10⁻⁷° C.⁻¹)74.0 26.8 25.7 15.6 CTE₂₂₋₁₀₀₀ by dilatometry (10⁻⁷° C.⁻¹) 76.7 30.728.1 21.6 Mean Lattice CTE₂₅₋₁₀₀₀ (10⁻⁷° C.⁻¹) 86.6 49.3 45.1 43.4Minimum Lattice CTE₂₅₋₁₀₀₀ (10⁻⁷° C.⁻¹) 69.3 2.4 −7 −23.4 Maximum CTEAnisotropy 34 99 115.2 136.8 Approximate Grain Size by SEM (μm) 31.6 7.85.5 4.3 Microcrack Index, Nb³ (Image Analysis) 0.34 0.41 0.19 0.28E_(25° C.) (10⁶ psi) 9.75 5.49 7.68 4.41 E_(1200° C.) (10⁶ psi) 15.814.1 13.8 13.6 E°_(25° C.) (10⁶ psi) 17.86 15.08 16.92 13.41 MicrocrackIndex, Nb³ (Elastic Modulus) 0.25 0.36 0.31 0.38 MOR (psi) 4871 41046755 2028 MOR/E (%) 0.050% 0.075% 0.088% 0.046% Estimated ThermalDown-Shock Limit (° C.) 100 391 472 380

TABLE 6 Crystal lattice coefficients of thermal expansion for zirconiumtin titanate compositions fired at 1600° C. Formula of Zirconium TinComposition Lattice CTE_(25-1000° C.) Values (10⁻⁷° C.⁻¹) Titanate PhaseCode CTE(a) CTE(b) CTE(c) CTE(avg) ΔCTE_(max) ZrTiO₄ D 69.3 103.3 87.186.6 34.0 ZrTi_(0.7)Sn_(0.3)O₄ E 85.5 37.9 63.7 62.4 47.6ZrTi_(0.4)Sn_(0.6)O₄ F 101.4 2.4 44.1 49.3 99.0 Zr_(0.75)TiSn_(0.25)O₄ G85.3 58.3 76.9 73.5 27.0 Zr_(0.75)Ti_(0.75)Sn_(0.5)O₄ H 88.2 35.9 47.357.1 52.3 ZrTi_(0.3)Sn_(0.7)O₄ L 104.1 −1.5 38.4 47.0 105.6ZrTi_(0.2)Sn_(0.8)O₄ M 108.2 −7.0 34.2 45.1 115.2Zr_(1.20)Ti_(0.60)Sn_(0.20)O₄ O 81.9 38.3 63.4 61.2 43.6Zr_(1.15)Ti_(0.41)Sn_(0.44)O₄ P 113.4 −23.4 40.3 43.4 136.8Zr_(1.13)Ti_(0.23)Sn_(0.64)O₄ Q 117.1 −26.5 29.8 40.1 143.6

According to exemplary embodiments of the present disclosure, the lowcoefficient of thermal expansion of the ceramic bodies is beneficial forthe thermal shock resistance. For example, when a long cylindricalceramic specimen that is at an initial temperature T₂ is suddenly cooledto a temperature T₁ at the surface, the surface is in tension, and thetensional stress, 6, is defined by the general equation:σ=Eε/(1−ν)  (Eq 9)

Where E is the elastic modulus of the ceramic, ε is the strain resultingfrom the shrinkage of the surface during cooling, and ν is Poisson'sratio. In the present case, the strain is defined by the differencebetween the length of the interior of the cylinder at T₂, L_(T2), andthe length that the surface of the cylinder would have at temperatureT₁, L_(T1), if it were unconstrained, relative to the initial length ofthe body at room temperature, L°:ε=(L _(T2) −L _(T1))/L°  (Eq 10)

To express Equation (10) in terms of the measured thermal expansion ofthe material, the equation may be rewritten as follows:

$\begin{matrix}\begin{matrix}{ɛ = {{\left\lbrack {\left( {L_{T\; 2} - {L\;{^\circ}}} \right) - \left( {L_{T\; 1} - {L\;{^\circ}}} \right)} \right\rbrack/L}\;{^\circ}}} \\{= {{\left( {{\Delta\; L_{T\; 2}} - {\Delta\; L_{T\; 1}}} \right)/L}\;{^\circ}}} \\{= {\left( {\Delta\;{L/L}\;{^\circ}} \right)_{T\; 2} - \left( {\Delta\;{L/L}\;{^\circ}} \right)_{T\; 1}}}\end{matrix} & \left( {{Eq}\mspace{14mu} 11} \right)\end{matrix}$

It will be recognized that the two terms (ΔL/L°)_(T2) and (ΔL/L°)_(T1)in Equation (11) represent two points on the thermal expansion (ΔL/L vs.T) curve for the material in question, at the temperatures T₂ and T₁. Atfailure, the tensional stress may be approximated by the modulus ofrupture, MOR:MOR=E[(ΔL/L°)_(T2)−(ΔL/L°)_(T1)]/(1−ν)  (Eq 12)Rearranging gives:[(ΔL/L°)_(T2)−(ΔL/L°)_(T1)]=MOR(1−ν)/E  (Eq 13)and(ΔL/L°)_(T2)=(ΔL/L°)_(T1)+MOR(1−ν)/E  (Eq 14)

To derive the thermal shock limit T₂, the value of T₁ must first beselected, and is chosen to equal the temperature of the minimum on theΔL/L vs. T curve, since this will result in the greatest strain for agiven T₂. For a CTE curve with no minimum, the lowest value of T₁ on theΔL/L vs. T curve is room temperature (RT), which is about 25° C. Theupper temperature limit T₂, which is the “thermal shock limit” for acylinder of the ceramic, can then be found by (1) noting the value of(ΔL/L°) on the thermal expansion curve at T₁ (zero ppm when T₁=25° C.),(2) adding to that the calculated value of MOR(1−ν)/E, which yields thevalue of ΔL/L° at T₂; and (3) locating the position of that ΔL/L° valueon the ΔL/L vs. T curve to identify the temperature, T₂, thatcorresponds to that point.

The thermal shock limits derived in this way are provided in Table 5 andthe curves used in their construction are depicted in FIGS. 11, 12, 13,and 14 for examples D6a, F6a, M6a, and P6a. A value of 0.20 for thePoisson's ratio was utilized in the calculations of these microcrackedmaterials. Calculations were made using the cooling CTE curves for eachsample. The predicted thermal shock limit for comparative example D6a is100° C. The reduction in CTE among the exemplary examples oftin-containing compositions results in an increase in the predictedthermal shock limit to between 380 and 475° C., substantially greaterthan that of the comparative example.

Low-expansion zirconium tin titanate ceramic bodies provided accordingto exemplary embodiments of the disclosure include a very high meltingpoint (superior to cordierite-containing ceramics), thermodynamicstability from room temperature to at least 1600° C. (in contrast toaluminum titanate, which is metastable below 1300° C.), and the absenceof a silicate phase (such as is present in cordierite, mullite+aluminumtitanate, Sr-feldspar+aluminum titanate, and cordierite+aluminumtitanate ceramics) that could react with catalysts or ash deposits whenthe inventive body is used as a catalytic converter or exhaust gasparticulate filter. Low-expansion zirconium tin titanate ceramic bodiesprovided according to exemplary embodiments of the disclosure may alsobe expected to exhibit excellent dimensional stability with repeatedthermal cycling to high temperatures.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present disclosurewithout departing from the spirit or scope of the disclosure. Thus, itis intended that the appended claims cover the modifications andvariations of this disclosure provided they come within the scope of theappended claims and their equivalents.

The invention claimed is:
 1. A microcracked ceramic body, comprising: greater than 50 wt % of a zirconium tin titanate phase; a microcrack density; and a dilatometric coefficient of thermal expansion (CTE) from 25 to 1000° C. of not more than 40×10⁻⁷° C.⁻¹ as measured by dilatometry.
 2. The ceramic body of claim 1, wherein the dilatometric CTE from 25 to 1000° C. is not more than 30×10⁻⁷° C.⁻¹.
 3. The ceramic body of claim 1, wherein the dilatometric CTE from 25 to 1000° C. is not more than 25×10⁻⁷° C.⁻¹.
 4. The ceramic body of claim 1, wherein the minimum lattice axial CTE (CTE_(min)) of the zirconium tin titanate phase is ≤30×10⁻⁷° C.⁻¹.
 5. The ceramic body of claim 4, wherein the CTE_(min) of the zirconium tin titanate phase is ≤0×10⁻⁷° C.⁻¹.
 6. The ceramic body of claim 1, wherein the CTE_(min) of the zirconium tin titanate phase is ≤−20×10⁻⁷° C.⁻¹.
 7. The ceramic body of claim 1, wherein the zirconium tin titanate phase is at least 80 wt % of the ceramic body.
 8. The ceramic body of claim 1, wherein the zirconium tin titanate phase is at least 95 wt % of the ceramic body.
 9. The ceramic body of claim 1, wherein the zirconium tin titanate phase is at least 99 wt % of the ceramic body.
 10. The ceramic body of claim 1, wherein the mol % of each of ZrO₂, SnO₂ and TiO₂ components in the zirconium tin titanate phase is expressed as 40≤Z≤65, 13≤S≤50, and 5≤T≤30, where Z=100(mol % ZrO₂)/(mol % ZrO₂+mol % SnO₂+mol % TiO₂), S=100(mol % SnO₂)/(mol % ZrO₂+mol % SnO₂+mol % TiO₂), and T=100(mol % TiO₂)/(mol % ZrO₂+mol % SnO₂+mol % TiO₂).
 11. The ceramic body of claim 10, wherein 40≤Z≤63, 15≤S≤45, and 5≤T≤27.
 12. The ceramic body of claim 1, wherein the microcrack density Nb³ is expressed as Nb³≥k₁[0.102+6.00×10⁴(CTE_(min))+1.23×10¹⁰(CTE_(min))²+8.38×10¹⁴(CTE_(min))³], wherein k₁ is at least 1.0, wherein the microcrack density Nb³ is at least one of (Nb³)IA and (Nb³)EM, and wherein (Nb³)_(IA) is the microcrack density Nb³ determined by image analysis and (Nb³)_(EM) is the microcrack density Nb³ determined by Young's modulus, wherein CTE_(min) is a minimum lattice axial coefficient of thermal expansion (CTE) from 25 to 1000° C. of the zirconium tin titanate phase, and CTE_(min) is in units of ° C.-1.
 13. The ceramic body of claim 12, wherein k₁ is at least
 2. 14. The ceramic body of claim 12, wherein k₁ is at least
 3. 15. The ceramic body of claim 1, wherein a grain size parameter in units of micrometers (μm), g, of the zirconium tin titanate phase fulfills the expression g≥k₂[4.15+1.99×10⁶(CTE_(min))+3.58×10¹¹(CTE_(min))²+2.15×10¹⁶(CTE_(min))³], wherein k₂ is at least 1, CTE_(min) is a minimum lattice axial coefficient of thermal expansion (CTE) from 25 to 1000° C. of the zirconium tin titanate phase, CTE_(min) is in units of ° C.⁻¹, and the grain size is determined by a line intercept method applied to an image of the ceramic microstructure and is defined as g=L/p where p is the number of grain boundaries intercepted by one or more straight lines of total length L or one or more circles of total circumference L, wherein L is in units of micrometers and L is chosen such that the value of L/g is at least 25 in order to provide adequate counting statistics for calculation of the grain size parameter.
 16. The ceramic body of claim 15, wherein k₂ is at least 1.5.
 17. The ceramic body of claim 15, wherein k₂ is at least
 2. 18. A microcracked ceramic body, comprising: a predominant phase of zirconium tin titanate; a microcrack density; and a dilatometric coefficient of thermal expansion (CTE) from 25 to 1000° C. of not more than 40×10⁻⁷° C.⁻¹ as measured by dilatometry; and a zirconium oxide-based baddeleyite phase that contains at least tin and titanium in solid solution, wherein the baddeleyite phase is characterized by a phase transformation from a monoclinic phase at low temperature to a tetragonal phase at higher temperature and wherein the transformation occurs below 1000° C.
 19. The ceramic body of claim 1, further comprising a honeycomb structure comprising a plurality of axially extending end-plugged inlet and outlet cells.
 20. A method of manufacturing a microcracked ceramic body, comprising: providing an inorganic batch composition comprising a zirconium oxide powder, a titanium oxide powder, and a tin oxide powder, wherein the median particle size of at least two of the oxide powders is at least 5 μm and wherein the sum of the weight percentages of the zirconium oxide powder, titanium oxide powder, and tin oxide powder is sufficient to provide more than 50 weight percent of a zirconium tin titanate phase in the microcracked ceramic body; mixing the inorganic batch composition together with one or more processing aid selected from the group consisting of a plasticizer, lubricant, binder, pore former, and solvent, to form a plasticized ceramic precursor batch composition; shaping the plasticized ceramic precursor batch composition into a green body; and firing the green body under conditions effective to convert the green body into the microcracked ceramic body comprising: greater than 50 wt % of the zirconium tin titanate phase, wherein the mol % of each of ZrO₂, SnO₂ and TiO₂ components in the zirconium tin titanate phase is expressed as 40≤Z≤65, 13≤S≤50, and 5≤T≤30, where Z=100(mol % ZrO₂)/(mol % ZrO₂+mol % SnO₂+mol % TiO₂), S=100(mol % SnO₂)/(mol % ZrO₂+mol % SnO₂+mol % TiO₂), and T=100(mol % TiO₂)/(mol % ZrO₂+mol % SnO₂+mol % TiO₂); wherein a minimum lattice axial CTE (CTE_(min)) from 25 to 1000° C. of the zirconium tin titanate phase is not more than 30×10⁻⁷° C.⁻¹; and wherein a zirconium tin titanate grain size parameter, g, in units of micrometers (μm) fulfills the expression g≥k₂[4.15+1.99×10⁶(CTE_(min))+3.58×10¹¹(CTE_(min))²+2.15×10¹⁶(CTE_(min))³], wherein k₂≥1, CTE_(min) is in units of ° C.⁻¹, and the grain size is determined by a line intercept method applied to an image of the ceramic microstructure and is defined as g=L/p where p is the number of grain boundaries intercepted by one or more straight lines of total length L or one or more circles of total circumference L, wherein L is in units of micrometers and L is chosen such that the value of L/g is at least 25 in order to provide adequate counting statistics for calculation of the grain size parameter. 